Recently formed wind slabs and touchy persistent weak layers are making for tricky conditions. Conservative terrain selection remains important.
Weather Forecast
On Tuesday and Wednesday morning expect a mix of sun and cloud and light northwest winds. By Wednesday evening a Pacific system will make its way inland bringing 3-5cm of new snow and strong southwest winds. Freezing levels will stay at valley bottom for the forecast period.
Avalanche Summary
On Saturday a size 3 sledder-triggered avalanche occurred in the Gorman Creek riding area near Golden. According to the report, 4 people were involved in the incident; however, all of the party member survived. Hats off to the sledders who responded to the incident in a calm and organized manner. Check-out the great Mountain Information Network report for details. On Monday, a size 2 wind slab was accidentally triggered by a skier in the backcountry around Golden. The individual was carried to the bottom of the slope, but was not buried or injured. Recently formed wind slabs and a reactive persistent slab are both expected to remain sensitive to human-triggering on Tuesday.
Snowpack Summary
40-60cm of snowfall has typically accumulated over the past week and weaknesses may still exist within or beneath this snow. Southwesterly winds have recently built wind slabs on the leeward side of ridge crests and behind terrain features on cross-loaded slopes. The persistent weak layer of surface hoar buried in early-January is now typically down 60-90 cm and has recently produced some large, destructive avalanches in the region. The layer is slowly getting harder to human trigger but is still quite reactive in snowpack tests and has the potential for wide propagations. In general, the lower snowpack below this layer is well settled and strong.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.